Rotary spark gap



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Patented Aug. 19, 1947 UNITED STATES PATENT orrice' ROTARY SPARK GAP Irving Sager, Deal, and Edward Wiler,

Belmar J.

Application April s, 194s, semi No. 482,356 11 calms. (ci. :i4- 41) (Granted under the act of amended April 30. 1928: 370 0. G. 757) The invention described herein may be manufactured and 'used by or for the Government for governmental purposes, without the payment. to us of any royalty thereon.

This invention relates to spark gaps, and more particularly to rotary spark gaps.

The primary object of our invention is to generally improve spark gaps, particularly rotary spark gaps of the so-called cage type.

It has been proposed to use a spark gap to key the transmitter of a pulse echo system. If a constant frequency pulse is wanted, it is advantageous to use a rotary spark gap so that the frequency of the pulse may be determined by the rotative speed and the number of electrodes on the rotor. A rotary spark gap has other advantages in that there are a considerable number' of electrodes, and the electrodes are cooled somewhat by rotation of the rotor, thus prolonging wear. It may be explained that metal is relatively rapidly dissipated or sputtered from the cathode but not from the anode, and inasmuch as there is only one stationary electrode, while there may be four, six, eight or more movable electrodes, it is best to use the movable electrodes as the cathode.

In spite of the foregoing precautions, the usel ful life of a rotary spark gap is greatly reduced by dissipation of metal from the rotating elec-v trodes, and it is accordingly a further object of our invention to minimize this loss. In accordance with our invention, the electrodes of the rotor are made in the form of round rods, and

these rods are rotated about their individual axes at the same time that they are revolved about the axis of the rotor.

A further object of the invention is to avoid the possibility of the electrode rod being so rotated as to present the same surface toward the stationary electrode during each revolution or each few revolutions of the rotor. It is accordingly a more specific object to provide a suitable mechanism to turn the electrode rods very slowly relative to the speed of rotation of the rotor as awhole.

To accomplish the foregoing and other objects y which will hereinafter appear, our invention resides -in the rotary spark gap element and their relation one to the other as are hereinafter more particularly described in the specification and sought to be defined inthe claims. The specification is accompanied by a drawing in which Figure 1 is a plan view of a, rotary spark gap embodying features of our invention;

Figure 2 is a front elevation of the same; Figure 3 is a transverse section taken in the y plane of the line 3-3 of Figure 2;

Figure 4 is a section Ataken in the plane of the line 4-4 of Figure 2;

Figure 5 isa section drawn to enlarged scale March v3, 1883, M

and taken approximately in the plane of the line 5 5 of Figure 2;

Figure 6 is anothery section drawn to enlarged' scale, and taken approximately in the plane of the line 6-6 of Figure 2; and

Figure 7 is a section showing a detail of the belt and pulley drive.

Referring to the drawing, and more particularly to Figure 6, the spark gap comprises a stationary electrode I-2, and a plurality of movable electrodes I4 cooperating therewith. The movable electrodes are carried by a disk I6, which is mounted on and rotated by a shaft I8. Referring to Figures 1 and 2, the shaft I8 is driven by an appropriate motor 20. For operation at a fixed pulse frequency, the motor 20 should be a constant speed motorl for example a synchronous motor. In the specific case here illustrated, the electrode rods I4 are carried between spaced disks I6 and 22 iixedly mounted on the shaft I8.

In accordance with the electrodes Il are round rods and are rotatably carried by the disks I6 and 2-2. Each rod is provided with a wheel 24 (Figure 5), and the said wheels all engage a wheel 26 which is disposed coaxially with shaft I8. 'I'he wheel 26 may conveniently be carried on the shaft I 8, but is frotatable thereon. It will be evident that by causing a slight relative movement between the wheel 26 and the shaft I6, the electrode rods I4 will wheels. That is, the wheels 24 are pinions act-4 ing as planet gears, and mesh with gear 26 acting as a sun gear.

We also prefer to make the differential rotation of the gear y26 and the rotor more denite and controllable by using external drive means for the purpose. Specifically, and referring to Figures 1 through 4 of the drawing, the bearings 26 and 30 which carry the main shaft I6 may be enlarged or extended to carry an auxiliary back shaft 32. A pulley 34, fast on shaft Ils, is belted by means of a belt 36 to a pulley 38, which is fast on back shaft 32. yAnother pulley 40 is fast on back shaft 32, and is connected by means of belt 42 to a pulley 44, which is loose on main shaft Ill.` The belts are preferably round rubber belts received in V-grooved pulleys, as shown in Figure '1. In Figure 5 it will be seen that the sun gear 26 is secured directly to the loose pulley 44, as by means of screws 46.

present invention, the I If ali of the pulleys are made equal in diameter. they will all turn in unison at equal speed. and there will be no relative movement of the sun gear and the rotor. The same is true if pulleys 24 and 44 are equal, and if pulleys 20 and 40 are equal. If, however, the diameter of the pulley 3B is altered very slightly relative to the diameter of the pulley Ill, the rotative speeds of the sun gear and th'e rotor will become slightly different. In practice, the change in diameter may be made as little as a few thousandths of an inch. In the present case. the diameter of pulley 38 is increased slightly, and the diameter of pulley l is decreased slightly, so that in net effect the speed of the sun gear is reduced slightly compared to the speed of shaft I8. 4 The effect is much the same as th'ough the sun gear and its pulley Il were held back from full speed rotation by the application of a limited amount of brake pressure, but the speed ratio is predictable and reliable.

It will be understood th'at other pulley arrangements may be used, and that various changes in diameter may be adopted. Three of the four pulleys may have the same diameter, with only one changed, or all may have different diameters. After adopting a slight difference in diameter, the lower or the upper pulleys may then be equally reduced or increased in diameter, if that should prove more convenient in any particular case. In fact, it is not necessary that the external drive be a pulley drive at all, as other mechanisms may equally well be employed, though' perhaps somewhat less conveniently.

Referring to Figure 4, itl will be seen that the loose pulley ll is, in the present case, mounted on main shaft I8 by means of an anti-friction ball bearing 48. This refinement is dispensable, though desirable when using an elastic belt such as those here employed.

Ball bearings are also preferably used for the back shaft 32 at posts 28 and 30, and for the mainshaft I8 at post 50. Another ball bearing may be used for the main shaft-i8 in eith'er the post 28 or the post 30, or, if desired, large clearance holes may be provided in these posts and the motor then used as a opposite end of the main shaft. In the one case, the coupling between the motor shaft and the main shaft IB may be a flexible coupling, andin the other case should be a rigid coupling.

The shafts I8 and 32, and the pulleys 34, 38, Il and 44 may be made of a suitable insulation material such as Bakelite. The bearings 2B, 30 and 50 and the base 52 on which they are mounted may also be made of Bakelite or like synthetic resin. The disks I6 and 22 of the rotor, as well as the collars 5l at one end of the electrodes ll, may be made of brass or other highly conductive metal. In fact, the sun and planet gears may also be made of brass because the relative rotative speed is slight and the tooth pressure is light. The electrode rods il are preferably made of tungsten, molybdenum. or other metal having similar high temperature characteristics. The stationary electrode l2 is similarly made of high temperature metal and may be ,mounted on a brass plate or slide 56. This is carried at the upper end of an insulation pedestal il, and its position is preferably made adjustable, as by means of a screw 60 received in a slot 82 in holder 56, thus making it possible to adjust the interelectrode spacing.

External connection to the stationary electrode may be made in any desired manner, as by bearing for the means of a soldering lug (not shown) received on the screw 80. External connection to the rotor may be obtained by means of a soldering lug (not shown) secured at a screw 64, which holds a leaf spring 88, the upper end of which is formed into a box-like holder 88 for a carbon block lll. Block 10 acts as a brush bearing against the projecting end of a metal rod 80 (Figure 6) running axially through the right-hand end portion (as viewed in Figures 1 and 2) of insulation shaft I8. The rounded projecting end of said rod ilsoshown in Figures i and 2 lust inside the block The rotor disks Il. and 22 are permanently secured to a metal spool-like hub 14 (Figure 6) having end flanges 18. A screw or pin or like metal connector 18 is driven through the hub 14 into the aforesaid center rod B0, thereby establishing the desired electrical connection between the rotor and the carbon block or brush 1l).

It is believed that the construction and operation of our improved rotary spark gap, as well as the advantages thereof, will be apparent from the foregoing detailed description thereof. The rotor has numerous electrodes, and is therefore preferably used as the cathode or consumed element of the spark gap. The life of each revolving electrode, and consequently of the entire structure, is greatly prolonged by slowly rotating the electrode relative to the rotor as the latter spins. In this way the entire peripheral surface of the cylindrical electrode is used, instead of only a thin strip of surface at one side of the cylinder. There is some slow wear of the stationary electrode, but after long use this may be replaced. In fact, the mounting of the revolving tungsten rods is such that these two may be replaced when worn, the collars and gears preferably being secured at the ends of the rods by releasable set screws.

It will be apparent that while we have shown and described our invention in a preferred form, many changes and modifications may be made in the structure disclosed without departing from the spirit of the invention, as sought to be dened in the following claims.

We claim:

1. ,A rotary spark gap comprising a stationary electrode, a rotor, said rotor including a disk and a plurality of electrode rods spaced about the periphery of the disk, the sides of said rods acting as movable electrodes for cooperation with the stationary electrode, a motor to drive the rotor,

and additional means to rotate the rods as they revolve with the rotor.

2. A rotary spark gap comprising a stationary electrode, a rotor, said rotor including circular end disks with a plurality of round electrode rods extending in axial direction between the disks and spaced about the periphery of the disks, the sides of said rods acting as movable electrodes for cooperation with the stationary electrode, a motor to drive the rotor, and additional means to rotate the rods as they revolve about the axis of the rotor.

3. A rotary spark gap comprising a stationary electrode, a rotor, said rotor including circular end disks with a plurality of round electrode rods extending in axial direction and spaced about the periphery of the disks, the sides of said rods acting as movable electrodes for cooperation with the stationary electrode, and means to rotate the rods as they .revolve about the axis of the rotor, said means operating in response to rotation of the rotor and being so arranged as to rotate the rods only a very small fraction of a revolution for each revolution of the rotor.

4. A rotary spark gap comprising a stationary electrode, a rotor, said rotor including circular end disks with a plurality of round electrode rods extending in axial direction and spacedv about the periphery of the disks, the sides of said rods acting as movable electrodes for cooperation with the stationary electrode, and means to 4rotate the rods as theyl revolve about the axis of the rotor, said means including a plurality of wheels secured to the ends of the electrode rods, and means for so cooperating with the Wheels as to turn the same relative to the rotor, during rotation of the rotor.

5. A rotary spark gap comprising a stationary electrode, a rotor, said rotor including circular end disks with a plurality of roundelectrode rods extending in axial direction and spaced about the periphery of the disks, the sides of said rods acting as movable electrodes for cooperation with the stationary electrode, and means to rotate the rods as they revolve about the axis of the rotor, said means including a large wheel coaxial with the rotor and engaging a plurality of small wheels secured to the ends of the electrode rods, and means for slowing or holding back the rotation of the large wheel slightly relative to the rotation of the rotor, whereby the resulting differential.

movement of the large wheel and the rotor causes a slow rotation of the electrode rods of the rotor.

6. A rotary spark gap comprising a stationary electrode, a rotor, said rotor including circular end disks with a plurality of round electrode rods extending in axial direction and spaced about the periphery of the disks, the sides of said rods acting as lmovable electrodes for cooperation with the stationary electrode, a motor, a shaft connecting the motor and the rotor, and means to rotate the rods as they revolve about the axis of the rotor, said means comprising a sun gear rotable relative to the shaft, a planet gear on each electrode rod, said planet gears meshing with said sun gear, and means to cause a slight difference in the rotative speed of the rotor and the sun gear whereby the electroderods are very slightly rotated as they are rapidly revolved with the rotor.

7. A rotary spark gap comprising a stationary electrode, a rotor, said rotor including circular end disks with a plurality of round electrode rods extending, in axial direction and spaced about the periphery of the disks, the sides of said rods acting as movable electrodes for cooperation with the stationary electrode, a motor, a shaft connecting the motor and the rotor, and additional means to rotate the rods as they revolve about the axis of the rotor, said means comprising4 a sun gear loosely rotatable on the shaft, a planet gear on each electrode rod, said planet gears meshing with said sun gear, and means including differential pulleys and belts between said shaft and said sun gear to rotate said sun gear at a speed slightly different from that of the shaft whereby the electrode rods are Very slightly rotated as they are rapidly revolved with the rotor.-I

8. A rotary spark gap comprising a stationary electrode, a rotor, said rotor including end disks with a plurality of electrode rods extending in axial direction and spaced about the periphery of the disks, the sides of said rods acting as movable electrodes for cooperation with the stationary electrode, a motor, a main shaft connecting the motor and the rotor, and additional means to rotate the rods as they revolve about the axis of the rotor, said means comprising a back shaft parallel to the main shaft, fast and loose pulleys on the main shaft, two fastpulleys on the back shaft respectively belted to said fast and loose pulleys on the main shaft, there being a very slight difference in diameter between at least two of the pulleys, in order to produce a slight differential movement of the loose pulley relative to the main shaft, a center wheel secured to the loose pulley, and wheels on each electrode rod, said latter wheels engaging said center wheel, whereby the electrode rods are very slightly rotated as they are rapidly revolved with the rotor.

9. A rotary spark gap comprising a stationary electrode, a rotor, said rotor including circular end disks with a plurality of round electrode rods extending in axial direction and spaced about the periphery of the disks, the sides of said rods acting as movable electrodes for cooperation with the stationary electrode, a motor, a main shaft connecting the motor and the rotor, and additional means to rotate the rods as they revolve about the axis of the rotor, said means comprising a back shaft parallel to the main shaft, fast and loose pulleys on the main shaft, two fast pulleys on the back shaft respectively belted to said fast and loose pulleys on the main shaft, there being a very slight difference in diameter between at least two of the pulleys, in order to produce a slight differential movement of the loose pulley relative to the main shaft, a sun gear secured to the loose pulley, and a planet gear on each electrode rod, said planet gears meshing with said sun gear, whereby the electrode rods are very slightly rotated as they are rapidly revolved with the rotor.

10. A rotary spark gap comprising a stationary electrode, a rotor, said rotor including circular end disks with a plurality of round electrode rods extending in axial direction and spaced about the periphery of the disks, the sides of said rods acting. as movable electrodes for cooperation with the stationary electrode, and means to rotate the rods as they revolve about the axis of the rotor, said means including a large wheel coaxial with the rotor and engaging a plurality of small wheels secured to the ends of the electrode rods, and means for causing rotation of the large wheel relative to the rotation of the rotor, whereby the resulting differential movement of the large wheel and the rotor causes rotation-of the electrode rods relative to the rotor.

l1. In the operation of a rotary spark gap comprising a rotor carrying electrode rods, the method of prolonging the life of the electrode rods which includes slowly rotating the rods about their axes as they are rapidly revolved by the rotor about the rotorv axis.

IRVING SAGER. A EDWARD WILER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,357,827 Sperry i--- Nov- 2, 1920 444,104 Reppy Jan. 6, 1891 519,283 Fyfe May 1, 1894 FOREIGN PATENTS Number Country Date 19,763 Great Britain Aug. 29, 1912 

